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Forensic Impressions Examination

When a perpetrator hides evidence of a crime, it’s commonly called “covering their tracks.” For instance, an individual burglarizes a home and uses a cloth to wipe away any fingerprints before leaving. He thinks he has covered his trail; but he may not realize the impressions his shoes or tires make could also be used to link him to the scene of the crime.

These footwear and tire track impressions are referred to as “pattern evidence” because the impressions form a unique pattern. Shoes and boots leave prints and impressions specific to their particular brand, style and size. The tread on each tire of a vehicle may provide investigators with similar information.

Footwear and tire tracks can be deposited on almost any surface, from paper to the human body. Prints are divided into three types: visible, plastic and latent.

A visible print is a transfer of material from the shoe or tire to the surface. This type can be seen by the naked eye without additional aids. For example, bloody shoe prints left on flooring or tracks left by muddy tires on a driveway.

A plastic print is a three-dimensional impression left on a soft surface. This includes shoe or tire tracks left in sand, mud or snow.

A latent print is one that is not readily visible to the naked eye. This type is created through static charges between the sole or tread and the surface. Examiners or investigators use powders, chemicals or alternate light sources to find these prints. Examples include shoeprints detected on a tile or hardwood floor, window sill, or metal counter, or tire tracks detected on road surfaces, driveways or sidewalks.